The present invention relates a method of manufacturing a fuel injection valve used for supplying fuel to various engines incorporated into an automobile. More particularly, the present invention relates a method of manufacturing a fuel injection valve by which fuel is whirled and supplied to a fuel injection path of a valve seat.
Conventionally, there is provided a fuel injection valve, the valve body of which is cylindrical, in which a valve such as a needle valve or ball valve is arranged and a valve seat having a fuel injection path is arranged at an outlet of the cylindrical valve main body, and fuel supplied from the outside the valve is whirled by a whirler so that fuel, which is supplied from the outside, can be fed to the fuel injection path. FIG. 4 is a cross-sectional view showing an example of the conventional fuel injection device in which the above fuel injection valve is used. FIG. 5 is an enlarged cross-sectional view of the fuel injection valve of the fuel injection device. FIG. 6 is an enlarged cross-sectional view of another fuel injection valve of the fuel injection device.
In FIG. 4, reference numeral 1 is a fuel injection device, reference numeral 2 is a housing body of the fuel injection device 1, and reference numeral 3 is a fuel injection valve which is supported by a lower end portion of the housing body 2 by means of calking. Reference numeral 4 is a fuel supply pipe, reference numeral 5 is a cylinder head of an engine, and reference numeral 6 is a valve operation device having an electromagnetic coil 61 and others for operating a needle valve 12 described later. A forward end portion of the fuel injection device 1 is inserted into a fuel injection device insertion hole 51 formed in a cylinder head 5 of the engine.
In FIG. 5, reference numeral 9 is a valve main body of the fuel injection valve 3, reference numeral 11 is a valve seat, reference numeral 12 is a needle valve, and reference numeral 13 is a whirler. The valve main body 9 is a cylindrical body having an insertion port 91 into which the needle valve 12 is inserted, a small diameter section 92 and a large diameter section 93. The valve seat 11 and the whirler 13 are fixed to the large diameter section 93 of the valve main body 9 which are arranged as shown in the drawing. At the center of the valve seat 11, there is provided a fuel injection path 10. At the center of the whirler 13, there is provided a valve body sliding hole 131. The needle valve 12 includes: an armature 121, a large diameter section 122, and a small diameter section 123 to be slid in the whirler. An outer diameter of the forward end section of the needle valve 12, which continues to the section 123 to be slid in the whirler, is gradually reduced, and the forward end section of the needle valve 12 enters the fuel injection path 10 and closes the entrance opening of the fuel injection path 10. An outer diameter of the large diameter section 122 is a little smaller than the inner diameter of the small diameter section 92 so that the large diameter section 122 can slide on the inner wall face of the small diameter section 92 of the valve main body 9. An outer diameter of the section 123 to be slid in the whirler is a little smaller than the inner diameter of the valve body sliding hole 131 so that the section 123 to be slid in the whirler can penetrate the valve main body sliding hole 131 of the whirler 13 and slide on the inner wall of the valve body sliding hole 131 of the whirler 13. Due to the foregoing, the entire needle valve 12 can go ahead and back in the valve main body 9 by the valve operation device 6 and armature 121 shown in FIG. 4 so as to open and close the fuel injection path 10 of the valve seat 11.
In this connection, in general, the whirler 13 can be inserted inside the large diameter section 93 of the valve main body 9 without being given any press-fitting pressure, however, the outer diameter of the whirler 13 is determined so that no clearance is substantially formed between the outer wall of the whirler 13 and the inner wall of the large diameter section 93 after the whirler 13 has been arranged in the large diameter section 93. On the other hand, the outer diameter of the valve seat 11 is determined so that a press-fitting pressure can be required when the valve seat 11 is inserted inside the large diameter section 93 of the valve main body 9. When the valve seat 11 is press-fitted inside the large diameter section 93, it can be fixed inside the large diameter section 93. At the same time, the valve seat 11 fixes the whirler 13 in the large diameter section 93.
The fuel injection valve 3 shown in FIG. 5 is manufactured in the following manufacturing process. First, the whirler 13 is inserted inside the large diameter section 93 of the valve main body 9 while the fuel introduction port face 132 is being directed to the forward end wall 921 of the small diameter section 92 of the valve main body 9, and then the valve seat 11 is press-fitted inside the large diameter section 93 until the fuel introduction port face 132 of the whirler 13 comes into contact with the forward end wall 921 of the small diameter section 92 of the valve main body 9. Due to the foregoing, the valve seat 11 is fixed inside the large diameter section 93 by the press-fitting pressure created by the valve seat 11 itself, and the whirler 13 is also fixed being interposed between the forward end wall face 921 of the small diameter section 92 and the valve seat 11. Finally, the needle valve 12 is inserted into the valve main body 9 from the insertion hole 91 of the valve main body 9, and the extreme end portion of the needle valve 12 penetrates the valve body sliding hole 131 of the whirler 13 and reaches the entrance opening of the fuel injection path 10.
In this connection, the valve main body 9, needle valve 12, whirler 13 and valve seat 11, which are used when the fuel injection valve 3 is manufactured by the above method, are previously designed so that these parts can have central axis A, which is shown in FIG. 5, in common. However, actually, the centers of these parts do not agree with central axis A because of the fluctuation of dimensional accuracy caused among the manufacturing lots. When the centers of these parts do not agree with central axis A, the following problems may be encountered. Since the whirler 13 and the needle valve 12 interfere with each other, it becomes difficult for the needle valve 12 to be inserted into the whirler. Even if the needle valve 12 can be inserted, the portion 123 of the needle valve 12 to be slid in the whirler 13 partially comes into contact with the inner wall of the whirler 13 in the valve main body sliding hole 131 as shown in FIG. 6 (refer to portion B in FIG. 6). Therefore, the yield and performance of products are affected as described later.
When the portion 123 of the needle valve 12 to be slid in the whirler 13 partially comes into contact with the inner wall of the whirler 13 in the valve body sliding hole 131, an uneven clearance is caused between the outer wall of the section 123 to be slid in the whirler and the inner wall of the valve body sliding hole 131 of the whirler 13. Accordingly, fuel can not be uniformly atomized, and further the extreme end portion of the needle valve 12 can not be appropriately set at the entrance opening of the fuel injection path 10. Therefore, it becomes impossible to appropriately open and close the fuel path 10, and the essential function of the fuel injection valve 3 can not be fully exhibited, or the essential function of the fuel injection valve 3 might be lost. In this connection, in order to prevent the section 123 of the needle valve 12 to be slid in the whirler from coming into partial contact with the valve main body sliding hole 131, the aforementioned clearance may be increased. However, when the clearance is increased, fuel can not be uniformly atomized. Therefore, it is not preferable to increase the clearance. When the dimensional accuracy of each of the aforementioned parts is enhanced, the manufacturing cost of the fuel injection valve 3 is raised, which is not preferable, either.
In view of the various problems caused by the prior art, it is an object of the present invention to provide a method of manufacturing a fuel injection valve 3 of high performance at a high yield by using parts such as a usual valve main body 9, needle valve 12, whirler 13 and valve seat 11, the dimensional accuracy of which is usual, in other words, by using parts, the dimensional accuracy of which fluctuates among the manufacturing lots in a usual way.
(1) The present invention provides a method of manufacturing a fuel injection valve comprising the steps of: inserting a guide pin into a cylindrical valve main body, the guide pin having an aligning forward end portion for aligning the guide pin with respect to a central axis of a fuel injection path of a valve seat, the guide pin also having an inserting section to be inserted into a whirler, the inserting section of the guide pin to be inserted into a whirler being inserted into a valve body sliding hole of the whirler which supplies fuel to the fuel injection path by whirling fuel, the inserting section of the guide pin to be inserted into the whirler having an outer diameter larger than an outer diameter of a section of the valve body to be slid in the whirler; arranging the whirler at the guide pin by inserting the section of the guide pin to be inserted into the whirler in the valve body sliding hole; fixing the valve seat at one end of the valve main body under the condition that a forward end of the guide pin is aligned with respect to the central axis of the fuel injection path; and pulling out the guide pin from the valve main body and arranging the section of the valve body to be slid in the whirler in the valve body sliding hole.
(2) In item (1), the outer diameter of the inserting section of the guide pin to be inserted into the whirler is larger than the outer diameter of the sliding section of the valve body to be slid in the whirler by at least 10% of the average of the clearance between the whirler and the section of the valve body to be slid in the whirler in the valve body sliding hole.
(3) In item (1) or (2), the outer diameter of the whirler is smaller than the inner diameter of the valve main body in a portion where the whirler is arranged by at least 10 xcexcm.
(4) In item (1), (2) or (3), the valve seat is fixed to an end of the valve main body by clearance-fitting.